The 12 Ultra is a rumored successor for the Xiaomi Mi 11 Ultra, a top-end Android smartphone that comes with a ceramic rear panel. Now, the alleged 2022 update is rumored to continue this trend - however, the OEM is now tipped to offer the flagship with alternative backing materials this year.
https://www.notebookcheck.net/Xiaomi-12-Ultra-A-new-leak-backs-multiple-different-premium-finishes-for-the-upcoming-super-flagship.611381.0.html